The resource availability scenario (RAS) is an important consideration when developing potential environmental water priorities, plans and watering actions over the year ahead.
The assessment of the RAS occurs leading up to and throughout the water year. The assessment is based climate conditions over the previous year (rainfall, runoff and soil moisture) and surface water available in storages and accounts. Recognition of the inflows to the catchment in the preceding water year are hence taken into account.
The scenarios indicate the overall strategy, objectives and types of watering actions that are likely given the current and forecast conditions.
For example, under dry conditions, the focus is strategic drought refuges, such as permanent freshwater holes that remain even when the surrounding area is dry and water is deliverable. While in wet conditions, managers often focus on enhancing natural high river or tributary flows and their connection to the floodplain and/or supporting waterbird breeding if triggered, fish spawning and movement, and building resilience into floodplain vegetation.
Frogs
Five resource availability scenarios (RAS) are used: very dry, dry, moderate, wet and very wet. The RAS is determined by looking at water likely to be in accounts 1 July from carryover and any new Available Water Determination (AWD) and the likely availability of the different types of planned environmental water (PEW). Determining the likely resource availability requires estimating water availability (account balances and any AWD at 1 July) and the antecedent conditions.
Current catchment conditions and the Bureau of Meteorology’s seasonal and longer-term forecasts are also taken into account to assess antecedent conditions.
And example of how the RAS is determined below:
Consider if the AWD for general security accounts at 1 July was 0%, with a median to high surface water availability due to water carried over from the previous water year (60% of total licensed entitlement available and Environmental Water Allowance available). A combination of below average rainfall (dry) with the persistence of water in the landscape from floods (wet) the previous year means the antecedent conditions can be best described as median. The likely RAS for the new water year would be moderate, with the possibility of becoming dry if the catchment enters a dry phase later in the water year.
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